Next execution statement not working in debug mode when using step into button

i am new to assembly and its file structure,
i am using stm32f103c6 along with St-link_v2

all i knew is code starts execution from reset handler, there system_init and __main functions are executed
when i am stepping into system init label then next execution statement(yellow arrow) is pointing to instructions in editor window and also into disassembly window
but when there is turn of __main label then, instead of stepping into __main label whole code gets executed like i have pressed run(f5),
when i use breakpoints at the starting of __main's first instruction then, i could see code execution step by step in disassembly window but not in main editor
if anyone has an idea what going on then it will be greatly helpful as
while debugging its more convenient to watch what going on by looking into steps of instruction written in editor
i have attached a video for better reference, first time i have used a breakpoint at __main label and one could see instruction execution in disassembly window,
second time there is no breakpoint then step into behaved like run(F5)

thanks

drive.google.com/.../view